Method for producing an assembly by friction welding

ABSTRACT

Cluster gear assemblies are produced by a method and apparatus which join a plurality of pre-machined gears by a common joining member. The plurality of gears are held in relative nonrotative relationship by special holding means which further establish precise angular and axial alignment between the gears and axial alignment between the joining member and the gears. Joining of the various members to produce the assembly is accomplished by friction welding.

United States Patent [1 1 Satzler et al.

[451 Aug. 7, 1973 METHOD FOR PRODUCING AN ASSEMBLY BY FRICTION WELDING[75] Inventors: Ronald L. Satzler, Metamora;

Marion R. Calton, East Peoria, both [73] Assignee: Caterpillar TractorCo., Peoria, 111.

[22] Filed: June 1, 1971 21 App1.No.: 148,780

[52] U.S. Cl 29/4703, 29/1592, 156/73, 228/3 [51] Int. Cl 823k 27/00[58] Field of Search 29/4703, 159.2; 228/2; 156/23 [56] References CitedUNITED STATES PATENTS 3,626,779 12/1971 Howard 29/1592 3,477,115 11/1969Martin et al. 29/4703 Primary ExaminerJ. Spencer Overholser AssistantExaminerRobert J. Craig Att0rney -Fryer, Tjensvold, Feix, Phillips &Lempio [57] ABSTRACT,

5 Claims, 7 Drawing Figures PATENTEB 3.750.23

sum 2 UF 4 INVENTORS RONALD L. SATZLER MARION R. CALTON ATTORNEYSPATENIEUAUB H913 3,750,263

INVENTORS RONALD L. SATZLER MARION R. CAL TON SHEET BF 4 INVENTORS L,SATZLER R. CALTON RONALD MARION ATTORNEYS BY W W ,w

PATENTED METHOD FOR PRODUCING AN ASSEMBLY BY FRICTION WELDING BACKGROUNDOF THE INVENTION Friction welding is a well-known method of joiningindividual pieces into an assembly. However, this method has beenlimited in the past to joining pieces which required no specific angularalignment between the individual pieces of the conpleted assembly, sinceit is extremely difficult to stop a rotating piece in an exact position.Because of this porblem, most assemblies which require angular alignmentbetween individual pieces are not joined by friction welding. Many suchassemblies are produced by machining the entire assembly from oneoriginal piece. One example of this type of assembly is a cluster gear.

Cluster gear assemblies form a necessary portion of most transmissionunits, although they are expensive to produce and add bulk and weight toa unit. Present technology for manufacturing cluster gears utilizes aforging process whereby a gear blank is forged from a single slug ofmetal. The gear teeth are not formed on the forging but are machined insubsequent machining operations. Much of the expense of producingcluster gear assemblies relates to the time-consuming method ofmachining teeth on adjacent gears specifically where those gearsnecessarily have different outside diameters. The teeth on the largestgear in the cluster can be machined by a fast and economical hobbingoperation. However, the teeth on the smaller gears in the clusterusually must be machined by slow and expensive shaping and shavingoperations. The extra bulk and weight are the result of providingclearance between the adjacent gears to accommodate various types ofcutting tools for machining the gear teeth.

SUMMARY AND OBJECTS OF THIS INVENTION Briefly described, this inventionrelates to a method of producing an improved cluster gear assembly. Toproduce this assembly, special holding means are provided to hold aplurality of individual premachined gear members in an exact angular andaxial position while a joining member is simultaneously friction weldedto each of the gear members. Friction welding of the conventional or theinertia type may be used. It is, therefore, an object of this inventionto overcome the above briefly-described problems by providing methodsand apparatus for joining a plurality of individual parts into anassembly.

It is also an object of this invention to join a plurality of memberswhich require angular alignment by a method in which no relative motionbetween the plurality of members is permitted.

It is another object of the invention to join a plurality of individualfinished, or semifinished, gears into a cluster unit.

It is a further object of this invention to construct an improvedcluster gear assembly which is lighter in weight and less costly toproduce than known cluster gear assemblies.

A still further object of this invention is an apparatus which will holdmembers to be joined in an exact angular and axial position.

It is also an object of the invention to form a cluster gear assembly byjoining the parts of the assembly by the friction or inertia weldingprocesses.

LII

These and other objects of the invention will become apparent to thoseskilled in the art upon examination of the following description of thepreferred embodiments thereof as depicted in the drawings, which areintended to illustrate but not restrict the scope of this invention. Itis recognized that other embodiments of the invention may be used andstructural changes may be made by those skilled in the art withoutdeparting from the scope of the present invention and the purview of theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevationillustrating one embodiment of a friction welding machine which may beused to practice the method of the present invention;

FIG. 2 is a fragmentary side view, partially in section, illustratingworkpiece holding fixture parts and apparatus constructed in accordancewith one embodiment of the invention;

FIG. 3 is a top plan view of the joining member of FIG. 2;

FIG. 4 is a cross-sectional view of a gear assembly joined in accordancewith another embodiment of the invention;

FIG. 5 is a cross-sectional view of another gear assembly joined inaccordance with one embodiment of the invention;

FIG. 6 is a cross-sectional view of a gear assembly joined in accordancewith still another embodiment of the invention;

FIG. 7 is a cross-sectional view of another gear assembly joined inaccordance with one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A friction welding machine,constructed in accordance with one exemplary embodiment of the presentinvention is indicated generally by the reference number 10 in FIG. 1 ofthe drawings. As illustrated, the friction welding machine 10 comprisesa frame or housing structure 12 for housing the various components ofthe machine. Within the housing of the machine, an electric motor 14powers a hydrostatic transmission generally denoted by referencenumberal 16. The hydrostatic transmission 16 includes a hydraulic pump18 and a hydraulic motor 20, operably connected by a manifold orconduits 22. The hydraulic motor 20 is connected to a spindle assembly24 which is mounted for rotation within the machine frame 12.

A rotary holding fixture 26 is mounted on the spindle assembly 24 androtates with the spindle. An exemplary workpiece WP-l is securely heldwithin the rotary fixture 26.

A second workpiece WP-Z is securely held in a nonrotary fixture 28attached to a tailstock fixture 30 which is mounted on the frame 12.

The tailstock fixture 30 is mounted for axial movement on the machineframe by a load cylinder assembly 32.

A pressure control circuit, not shown, regulates the pressure in theload cylinder and thus determines the force with which the parts WP-land WP-2 are engaged.

The hydrostatic transmission assembly 16 can be used to vary the driveratio between the motor and the spindle assembly 24 and can also be usedto effectively disconnect the spindle assembly from the motor. Variousother means could also be used to disconnect the spindle from the motor,including many types of available clutches.

It is to be understood that flywheel weights, although not shown, couldbe mounted to the rotary holding fixture 26 so that the welding machinecan be operated as an inertia welding machine, as described in US. Pat.No. 3,273,233, and as further described in detail below. It is also tobe understood that the workpieces WP-l and WP-2 shown in FIG. 1 areexemplary only and do not necessarily represent the exact configurationof the workpieces to be welded within the scope of this invention. Amore detailed description of several workpiece configurations will begiven with reference to FIGS. 2, 3, 4 and 5 in the drawings.

With continued reference to FIG. 1, a welding operation for joining twoworkpieces WP-l and WP-2 together is performed by operating the machinein the following general manner:

One of the workpieces, WP-l, is secured within the rotatable holdingfixture 26 on the spindle assembly 24. The other workpiece, WP-Z, issecured within the nonrotatable holding fixture 28 which is furtherfastened to the tailstock assembly 30. The load cylinder 32 is thenactivated to move the tailstock assembly 30 toward the spindle 24 untilthe workpieces WP-l and WP-2 are in close proximity, but are not incontact with each other. The motor 14 is then activated and the spindleassembly 24 and rotatable holding fixture 26 are accelerated by means ofthe hydrostatic transmission assembly 16 which is coupled to theelectric motor 14.

When the predetermined and preset velocity is reached by the rotatingfixture 26, appropriate controls shut down or disconnect the electricmotor 14 from the spindle assembly 24, and at the same time activate theload cylinder 32 to move the tailstock fixture 30 forward. workpieceWP-2 is thereby brought into contact under pressure with the rapidlyrotating workpiece WP-l, and heat is generated by friction at thecontacting surfaces of the two workpieces. This heating continues untilthe workpieces reach the weld temperature at which time the upsettingpressure, applied by the load cylinder 32 at a constant or varyingpressure, causes flashing or upsetting to occur. During this period ofheating and flashing, the rotational velocity of the spindle and holdingfixture has continued to decrease.

At the time that rotation ceases, all of the stored energy in therotating members has been converted to heat and forging at the weldinterface and the weld is completed. The load cylinder 32 is thenactivated in a 7 reverse direction and the complete welded assembly isremoved from the holding fixtures of the machine. Although ths inertiawelding process has been described, it is recognized that other methodsof friction welding may be used to practice the instant invention.

FIG. 2 illustrates one embodiment of the present invention consisting ofa welded cluster gear assembly. The cluster gear assembly consists of afirst premachined gear 40, a second premachined gear 42, and a rotatablejoining member 44 which serves to join all members together into asassembly.

The two gears 40 and 42 are held together in a special nonrotatablefixture 28.

The rotatable joining member 44 is held in a special rotatable holdingfixture 26.

Fixture 28 is in turn securely fastened to the tailstock portion 30 of awelding machine.

Fixture 26 is securely fastened to the rotatable spindle of a frictionwelding machine (refer to H6. 1).

At this point, it should be stated that it would be possible, and insome instances desirable, to rotate the gears 40 and 42, by rotatingfixture 28 and hold the joining member 44 against rotation. The onlyrequirement is that relative rotary motion be imparted between theplurality of members (gears, in this case) and the joining member.

Fixture 28 contains two counterbores 46 and 48 with internal teeth 50and 52 machined in the respective counterbores. Internal teeth 50 aremachined to match and mesh with the external teeth 54 of gear 40, andinternal teeth 52 are machined to match and mesh with external teeth 56on gear 42. In this way, both gears 40 and 42 are prevented fromrotating and any angular alignment between the two gears can be obtainedby machining the internal teeth in the fixture 28 to produce the desiredalignment. Axial alignment between gears 40 and 42 is also attained byproper machining of the counterbores and internal teeth of fixture 28.

The joining member 44 is essentially a tubular member with an internalbore 58 which closely matches the bore 60 of gear 40.

The member 44 further contains a plurality of flats 62, which togetherform a hexagonal shape and fit into a matching socket 64 of the holdingfixture 26. In this way, the joining member 44 is securely held withinthe fixture 26 without the necessity of tightening any type of collector jaws.

Although the joining member and fixture socket have been indicated ashaving a hexagonal configuration, any number of other types ofconfigurations would work equally satisfactorily, such as square oroctagonal. The end of the joining member opposite the hexagonal portionis of reduced diameter and contains a circular projection 66 which isslightly smaller in diameter than the internal bore 68 of gear 42. Inthis way, the projection 66 extends through the bore 68 and contactssurface 70 of gear 40 without making contact with the internal bore 68of gear 42. The length of projection 66 is such that when it is insertedinto bore 68 of gear 42, the end of the projection will contact surface70 at or about the same time that contact is made between surface 72 ofthe joining member and surface 74 of gear 42.

At the beginning of a welding operation to join the two gears and thejoining member into a cluster gear assembly, a small gap exists betweenthe projection 66 and surface 70 as well as between surfaces 72 and 74.In this way, the joining member can be accelerated to the welding speedwithout friction developing due to contacting surfaces. However, oncethe welding velocity has been reached, the load cylinder is activated tobring the rotating joining member into contact with both nonrotatinggears 40 and 42. A weld is thereby accomplished between projection 66 ofthe joining member and the surface 70 of gear 40, and between surface 72of the joining member and surface 74 of the gear 42. Although no actualweld exists between the two gears 40 and 42, they are rigidly joined bythe member 44 since a separate area of the joining member 44 is weldedto each of the gears 40 and 42.

During the application of the welding thrust force, gear 40 is supportedby a projection 76 within fixture 28, and gear 42 is supported againstthe thrust by the gear 40.

A camber 78 on gear 42 forms a flash trap to accommodate the externalflash produced between the joining member 44 and gear 40.

Likewise, a machined groove 80 in the joining member 44 accommodates theinternal flash produced between member 44 and gear 42.

The external flash produced when surface 72 of member 44 is welded tosurface 74 of gear 42, can remain on the gear assembly since it is in anarea which will cause no problems. However, the internal flash producedbetween member 44 and gear 40, which will flow into the bores 58 and 60,will need to be removed since these bores must accommodate a shaft-Thisflash removal will present no problem since these bores must be finishmachined prior to final assembly of the cluster gear unit into atransmission.

FIG. 3 illustrates a top plan view of the joining member shown in FIG.2. As previously mentioned, the joining member 44 is provided with ahexagonal shape by flats 62 for easy insertion into and removal from therotatable holding fixture 26. The hexagonal portion 62 in cooperationwith socket 64 provides a positive driving connection between thejoining member 44 and fixture 26 during acceleration and to absorb thetorque developed during the friction welding operation.

Alternatively, joining member 44 could be held in any suitable manual orpower-operated chucking device to eliminate the necessity of producing anoncircular shape at the one end of the joining member.

Since the teeth of the two gears 40 and 42 are machined prior towelding, no extra space is required between the gears to accommodatemachining tools, as is required in the production of most cluster gearassemblies. This advantageously results in a high-strength, compact,lightweight assembly as compared with cluster gear assemblies producedby other methods. The total cost of producing a cluster gear assembly bythe instant invention is also less than other known methods since lesscostly machining operations can be used to machine the gears beforewelding.

Referring to FIG. 4 of the drawings, a slightly different embodiment ofthe invention is illustrated. In this embodiment, a joining member 86 isused to join three separate gear members 88, 90 and 92 into a clusterassembly. In this assembly three surfaces 94, 96, and 98 of the joiningmember are welded to respective surfaces 100, 102, and 104 of gears 88,90, and 92.

Small pockets 106 in the joining member and grooves 108 in gears 88, 90,and 92 cooperate to form flash traps for the flash produced during thewelding.

Any required angular alignment between gears 88, 90, and 92, can, ofcourse, be provided by a special holding fixture, similar to fixture 28in FIG. 2. Axial alignment between all members of the assembly isprovided by the two fixtures holding the rotary and nonrotary members. Acentral bore 112 in the joining member 86 can provide for the mountingof the completed assembly on a shaft.

FIG. 5 illustrates an alternate assembly joined in accordance with theembodiment shown and described in reference to FIG. 2. However, thecompleted assembly of FIG. 5 comprises a herringbone gear rather than acluster assembly. The herringbone gear assembly 116 consists of twohelical gears 118 and 120 and a joining member 122. In this assembly,surface 124 of joining member 122 is welded to surface 126 of gear 118and surface 128 of member 122 is welded to surface 130 of gear 120.

The herringbone gear is a very special type of gear and is extremelyexpensive to produce using present manufacturing technology. However, byjoining two premachined helical gears, one left hand and one right hand,using the methods and apparatus of the present invenlion, an inexpensiveherringbone gear is produced.

FIGS. 6 and 7 illustrate alternate designs, respectively, of a clustergear assembly 136 and a herringbone gear assembly 138 produced inaccordance with the present invention. Assembly 136 comprises a joiningmember 140 and three gear-like members, 142, 144 and 146. An outerconical-shaped surface 148 of the joining member 140 contains aplurality of longitudinally spaced parallel projections 150, 152 and154, which extend radially outward.

Member 142 contains two radially extending parallel end surfaces 156 and158, a central tapered bore 160, and a projection 162 extending radiallyinward from the central bore. Member 144 also contains two radiallyextending parallel end surfaces 166 and 168, a central tapered bore 170,and a projection 172 extending radially inward from the central bore.Likewise, member 146 contains two radially extending parallel endsurfaces 176 and 178, a central tapered bore 180 and a projection 182extending radially inward from the central bore.

The three projections 162, 172 and 182 contain respectively taperedsurfaces 184, 186 and 188 which match tapered surfaces 190, 192 and 194,respectively, ofjoining member projections 150, 152, and 154. Thejoining members 140 and the three gear members 142, 144, and 146 arewelded into assembly 136 by the previously described method wherein thethree gear members are held in a non-rotating fixture (not shown) andthe joining member is held in the rotatable fixture of a frictionwelding machine (not shown).

A special non-rotating holding fixture will secure the three gearmembers 142, 144 and 146 in whatever angular alignment is desired. Oncesecured in the fixture, surface 158 of member 142 is in contact withsurface 166 of member 144 and surface 168 of member 144 is in contactwith surface 176 of member 146. Actual welding between the joiningmember and the other members takes place at the contact areas betweentapered surfaces 184, 186 and 188 of the gear members and matchingtapered surfaces 190, 192 and 194 of the joining member.

In the completed assembly, two sealed pockets 196 and 198 are formedbetween joining member and the other members. Much of the flash producedduring welding will be contained within these pockets and will, ofcourse, need not be removed. Likewise, the flash at the other weldareas, which is not sealed within pockets 1.96 and 198, is in a recessedarea and will, most likely, not require removal.

FIG. 7 illustrates the design of FIG. 6 adapted to a herringbone gearassembly 138. In this embodiment, a left hand helical. gear member 202and a right hand helical gear member 204 are held in a non-rotatablefixture (not shown) while a joining member 206, held in the rotatableportion of a friction welding machine (not shown) is welded to the twogear members. As in the embodiment of FIG. 6, welding takes placebetween matching tapered surfaces on projections 208 and 210 of members202 and 204 and projections 212 and 214 of joining member 206.

While the subject invention has been illustrated and described withparticular reference to cluster gear assemblies, it is to be understoodthat other types of assemblies could be joined by using the disclosedmethod and apparatus. Therefore, we do not wish to be limited to theprecise details set forth, but desire to avail ourselves of such changesand alternations which fall within the purview of the following claims.

What is claimed is:

l. A method of joining a plurality of members comprising the steps of:

a. Locating a first joining member in a first workpiece holding means;

b. Locating at least second and third premachined gear members inrelative nonrotative relationship and precise axial alignment in asecond workpiece holding means;

c. lnterlocking internal peripheral elements of the holding means withexternal peripheral gear teeth of the second and third gear members tomaintain the second and third gear members in a fixed angular positionwith respect to each other;

d. Each of said second an third gear members having an annular surfaceexposed for contact with a surface on the first member;

e. Positioning one of sai'd workpiece holding means relative to theother workpiece holding means such that said first member is located ina predetermined axial position and in juxtaposed relationship to said atleast second and third members; and

f. Friction welding said first member to said second and third membersto form a cluster gear assembly.

2. A method as set forth in claim 1 wherein the said second and thirdmembers are premachined helical gears and said assembly is a herringbonegear assembly.

3. A method as set forth in claim 1 wherein the said friction weldingcomprises at least two separate weld areas disposed in different planesand the welds are accomplished simultaneously.

4. A method as set forth in claim 3 wherein said friction welding is ofthe inertia type in which the energy necessary to accomplish the weldingis stored in rotating flywheels.

5. A method as set forth in claim 1 wherein said first joining memberand one of said second and third gear members have bores extendingtherethrough which are coaxially arranged to form an axial passagethrough the gear assembly, an annular bond being formed between saidfirst joining member and said one of said second and third gear membersadjacent the axial bore formed through the gear assembly.

1. A method of joining a plurality of members comprising the steps of: a. Locating a first joining member in a first workpiece holding means; b. Locating at least second and third premachined gear members in relative nonrotative relationship and precise axial alignment in a second workpiece holding means; c. Interlocking internal peripheral elements of the holding means with external peripheral gear teeth of the second and third gear members to maintain the second and third gear members in a fixed angular position with respect to each other; d. Each of said second an third gear members having an annular surface exposed for contact with a surface on the first member; e. Positioning one of said workpiece holding means relative to the other workpiece holding means such that said first member is located in a predetermined axial position and in juxtaposed relationship to said at least second and third members; and f. Friction welding said first member to said second and third members to form a cluster gear assembly.
 2. A method as set forth in claim 1 wherein the said second and third members are premachined helical gears and said assembly is a herringbone gear assembly.
 3. A method as set forth in claim 1 wherein the said friction welding comprises at least two separate weld areas disposed in different planes and the welds are accomplished simultaneously.
 4. A method as set forth in claim 3 wherein said friction welding is of the inertia type in which the energy necessary to accomplish the welding is stored in rotating flywheels.
 5. A method as set forth in claim 1 wherein said first joining member and one of said second and third gear members have bores extending therethrough which are coaxially arranged to form an axial passage through the gear assembly, an annular bond being formed between said first joining member and said one of said second and third gear members adjacent the axial bore formed through the gear assembly. 